Device Role is an important step for configuring Meshtastic.
For most nodes, we recommend Client role. This is the "default" role and provides access to all features.
Client_Mute is a good choice for additional nodes, especially those in close proximity (e.g. a single home or apartment) or areas with high mesh coverage. These nodes can still send and receive messages but do not participate in routing other nodes' messages. They do not contribute to the mesh, but also do not contribute to the network burden that comes with multiple nodes in a very small area rebroadcasting a single message all at once.
Router or Repeater roles should only be used for devices that are exceptionally well located with excellent line of sight. Too many routers/repeaters can actually degrade mesh network performance, especially in dense meshes like within Chicago.
Other roles exist for nodes that serve a purpose other than messaging.